1. Field of the Invention
The present invention relates to a method and apparatus for processing random access and uplink transmission of a User Equipment (UE) in a mobile communication system. More particularly, the present invention relates to a method and apparatus for performing random access and uplink transmission of the UE supporting Carrier Aggregation (CA) efficiently.
2. Description of the Related Art
Mobile communication systems have been developed to provide subscribers with voice communication services on the move. With the rapid advance of technologies, the mobile communication systems have evolved to support high speed data communication services as well as standard voice communication services.
Currently, the next generation mobile communication system of the 3rd Generation Partnership Project (3GPP), known as the Long Term Evolution (LTE) system, is under development. The LTE system is a technology for implementing high-speed packet-based communication at about 100 Mbps. Recently, an LTE-Advanced (LTE-A) system is actively discussed as an evolution of the LTE system with new techniques to increase data rate. Hereinafter, both the legacy LTE system and the LTE-A system are referred to as the LTE system. The LTE system employs carrier aggregation to meet broader bandwidth requirements. Carrier aggregation is a technology for a User Equipment (UE) to transmit/receive data over multiple carriers. In detail, the UE transmits/receives data in cells using aggregated carriers (cells under the control of the same evolved Node B (eNB)). This means that the UE transmits/receives data in multiple cells.
Typically, a UE attempts random access to set up initial connection to a certain communication network. In a certain mobile communication system such as the LTE system, a random access process is used for another purpose, e.g., buffer state report and uplink transmission timing synchronization acquisition, as well as an initial access. In a case when the UE in a connected state performs random access, the UE may encounter a situation where the uplink transmission is required simultaneously with another ongoing uplink transmission or another random access attempt. More particularly, when the UE is operating in carrier aggregation mode, such situation is likely to occur more frequently. Therefore, a need exists for a method of a UE to perform random access regardless of ongoing uplink transmission.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.